Regulating defects in sulfur-doped Bi4O5I2 and constructing S-scheme heterojunctions with g-C3N4 to enhance photocatalytic antibiotic degradation

Photocatalysis technology presents a promising green pathway for eliminating antibiotic residues, however, the current performance falls short of practicality. A solvothermal method was employed to successfully prepare sulfur-defect-modified Bi4O5I2/CN S-scheme heterojunction composites in this work, which exhibit remarkable efficacy in the degradation of tetracycline antibiotics under visible light. Compared with Bi4O5I2, the optimized S-Bi4O5I2/CN(10 %) exhibited the best photocatalytic degradation performance of tetracycline hydrochloride (TC, 50 mg/L), achieving a 100 % degradation rate within 10 min. Additionally, it exhibited the broad applicability of the photocatalyst in practical application, effectively degrading various tetracycline antibiotics and maintaining good degradation efficiency across a wide range of pollutant concentrations and pH fluctuations. The catalyst is highly resistant to anion interference and achieves efficient degradation in a fixed-bed reactor, exhibiting high sensitivity. The composition of S-scheme heterojunctions was confirmed through XPS electron transfer, radical quenching experiments, and DFT theory calculations, while the intricate reaction mechanism occurring at the heterojunction interface of S-Bi4O5I2 and g-C3N4 was also elaborated. The degradation path of TC was investigated by using LC-MS and the toxicity assessments and mung bean germination experiments against byproducts also indicate the photocatalytic process can effectively decrease the toxicity and the potential risk of TC to the environment. This work presents a feasible and effective approach to enhance the photocatalytic performance of Bi4O5I2 through heterogeneous structure construction, demonstrating outstanding practical application in eliminating antibiotic residues in the environment.